Motor-driven compressor

ABSTRACT

There is provided a motor-driven compressor including a semiconductor device that comprises a compression mechanism, a motor, a housing, a wall, an electronic component, and a resin member. The motor drives the compression mechanism. The housing accommodates therein the compression mechanism and the motor. The wall extends from an outer surface of the housing so as to surround a part thereof and have an opened end and cooperates with the outer surface of the housing to form a casing. The electronic component is accommodated in the casing and includes a semiconductor module that includes a circuit board connected to the outer surface of the housing and a semiconductor element mounted to the circuit board. The resin member seals an entirety of the electronic component in the casing.

BACKGROUND OF THE INVENTION

The present invention relates to a motor-driven compressor including a semiconductor device that drives a motor of the motor-driven compressor.

Japanese Patent Application Publication No. 2003-322082 discloses a motor-driven compressor having a compression mechanism, a motor driving the compression mechanism, and a semiconductor device including a drive circuit driving the motor. The semiconductor device has transistor modules that are fixed to a housing of the motor-driven compressor by bolts through a resin insulation sheet.

A semiconductor device generates heat during its operation. The heat may cause thermal stress which in turn causes peeling at a connection part between a semiconductor element and a circuit board. In order to address such problems of the motor-driven compressor mounting the semiconductor device on the motor-driven compressor, effective measures need to be taken to ensure reliability of the semiconductor device that drives the motor of the motor-driven compressor.

The present invention, which has been made in light of the above problems, is directed to providing a motor-driven compressor including a semiconductor device that improves its reliability.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, there is provided a motor-driven compressor including a semiconductor device that comprises a compression mechanism, a motor, a housing, a wall, an electronic component, and a resin member. The motor drives the compression mechanism. The housing accommodates therein the compression mechanism and the motor. The wall extends from an outer surface of the housing so as to surround a part thereof and have an opened end and cooperates with the outer surface of the housing to form a casing. The electronic component is accommodated in the casing and includes a semiconductor module that includes a circuit board connected to the outer surface of the housing and a semiconductor element mounted to the circuit board. The resin member seals an entirety of the electronic component in the casing.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a perspective view of a motor-driven compressor having a semiconductor device according to an embodiment of the present invention; and

FIG. 2 is a longitudinal sectional view of the compressor of FIG. 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following will describe a semiconductor device mounted on a motor-driven compressor according to an embodiment of the present invention with reference to FIGS. 1 and 2. Referring to FIG. 1, the motor-driven compressor that is designated by reference numeral 10 includes a housing 11. The housing 11 accommodates therein a compression mechanism 12 compressing refrigerant and discharging refrigerant and a motor 13 driving the compression mechanism 12. The housing 11 is formed with an inlet 14 through which refrigerant is flowed into the housing 11. The motor-driven compressor 10 further includes a semiconductor device 15 for driving the motor 13. The semiconductor device 15 serves as an inverter for converting DC power to AC power and supplying the AC power to the motor 13.

The housing 11 has a wall 17 formed integrally with the housing 11 and extending from the outer surface 16 of the housing 11. In the present embodiment, the wall 17 is formed annularly at one end of the housing 11 adjacent to the motor 13. The wall 7 has an opened end 18. Therefore, a circular recess is formed at a part of the outer surface 16 of the housing 11 by the wall 17 and has a bottom that is formed by a part of the outer surface 16 at the one end of the housing 11.

As shown in FIG. 2, electronic components 19 that form the semiconductor device 15 are accommodated in the recess of the wall 17. The electronic component 19 includes a semiconductor module 20. The semiconductor module 20 includes a semiconductor element 21 and a circuit board 22 mounting thereon the semiconductor element 21. The semiconductor element 21 includes a switching element such as an IGBT (Insulated Gate Bipolar Transistor) and a diode.

The circuit board 22 includes a ceramic board 23 that serves as an insulating layer, a first metal plate 24 that is connected on the first surface of the ceramic board 23 and serves as a wiring layer, and a second metal plate 25 that is connected on the second surface of the ceramic board 23 that is located on the side of the ceramic board 23 opposite to the first surface and serves as a connection layer. The semiconductor element 21 is soldered to the first metal plate 24 and the second metal plate 25 is connected by brazing directly on the outer surface 16 of the housing 11 of the recess surrounded by the wall 17. The second metal plate 25 is brazed to the outer surface 16 of the housing 11. The ceramic board 23 is made of, for example, aluminum nitride. The first metal plate 24 and the second metal plate 25 are made of, for example, pure aluminum such as aluminum for industrial use having 99.0% purity or higher, or copper.

In the present embodiment, the second metal plate 25 serves as a stress reducing member reducing the stress applied to the connection between the circuit board 22 and the semiconductor element 21 and the connection between the circuit board 22 and the housing 11. The stress reducing member disperses the thermal stress caused by the difference of linear thermal expansion coefficient among the ceramic board 23, the first metal plate 24, the second metal plate 25, and the housing 11 thereby to reduce thermal stress applied to the above connections, namely the connection between the circuit board 22 and the semiconductor element 21 and the connection between the circuit board 22 and the housing 11. Though not shown in the drawing, the second metal plate 25 has therein a space in the form of a step, a groove, or a recess forming a part of the second metal plate 25 that is not connected to the housing 11 and hence helps reduce or relieve the thermal stress.

As described above, the wall 17 of the housing 11 forms a casing 26 housing the electronic components 19 including a semiconductor module 20. In other words, a space that is defined by the wall 17 and a part of the outer surface 16 of the housing 11 surrounded by the wall 17 serve as a casing for the semiconductor device 15.

As shown in FIG. 2, the casing 26 is sealed by a resin member 27 with the electronic components 19 housed in the casing 26. In the present embodiment, the resin member 27 sealing the casing 26 is made of epoxy resin.

The resin member 27 fills the space surrounded by the wall 17 to the opened end 18 of the wall 17. Thus, the electronic components 19 housed in the casing 26 are covered entirely by the resin member 27. The resin member 27 is not covered, but exposed to the atmosphere at the opened end 18 of the wall 17.

The following will describe the operation of the semiconductor device 15 for the motor-driven compressor 10. The semiconductor module 20 housed in the casing 26 is cooled by refrigerant flowing in the housing 11 of the motor-driven compressor 10. In the present embodiment wherein the circuit board 22 of the semiconductor module 20 is brazed directly to the outer surface 16 of the housing 11, heat exchange is performed easily between the refrigerant flowing in the housing 11 and the circuit board 22. Additionally, in the structure wherein the casing 26 is sealed by the resin member 27, thermal deformation at the connection between the semiconductor element 21 and the circuit board 22 and between the circuit board 22 and the housing 11 is suppressed and hence reduced.

The present embodiment offers the following advantageous effects.

(1) Sealing the casing 26 housing therein the electronic component 19 including the semiconductor module 20 by a resin member suppresses the thermal deformation. Therefore, the connection between the semiconductor element 21 and the circuit board 22 and the connection between the circuit board 22 and the housing 11 are prevented from being peeled by thermal stress, so that the reliability of the semiconductor device 15 is improved.

(2) Additionally, sealing the casing 26 by the resin member 27 improves the connection between the housing 11 and the semiconductor module 20, so that heat radiation of the semiconductor device 15 is improved. The reliability in the strength of the connection between the semiconductor element 21 and the circuit board 22 and the connection between the circuit board 22 and the housing 11 is improved, with the result that the reliability of the semiconductor device 15 is improved and, therefore, the deterioration of the semiconductor device 15 is suppressed.

(3) The configuration in which the semiconductor module 20 is connected directly to the housing 11 allows the semiconductor device 15 to be simplified in structure and be made smaller in size.

(4) The configuration in which the casing 26 is formed by the wall 17 of the housing 11 allows the wall 17 to serve as a jig that regulates the flow of resin when sealing the casing 26 by the resin member 27. Therefore, no jig need to be prepared for regulating the flow of resin and the sealing operation is made easily.

(5) The configuration in which the wall 17 forms a casing for the semiconductor device 15 allows the motor-driven compressor 10 to be simplified in structure and be made smaller in size as compared to a case in which a separate semiconductor device having therein the electronic component 19 is mounted on the housing 11.

(6) The wall 17 that is formed integrally with the housing 11 when making the housing 11, so that strength of the semiconductor device 15 including a casing is secured.

(7) In the semiconductor device 15, the second metal plate 25 of the circuit board 22 serves as stress reducing member. The provision of this stress reducing member in addition to the resin member 27 helps prevent the connection from being peeled.

(8) The circuit board 22 is brazed to the housing 11 and therefore the connection between the circuit board 22 and the housing 11 is improved. As a result, heat radiation of the semiconductor device 15 is improved.

The present embodiment may be modified as follows. For connecting the semiconductor module 20 to the housing 11, a bolt, pressure welding and so on may be used.

The layout and the number of the casing 26 may be changed. For example, the casing 26 may be formed extending from the outer peripheral surface of the housing 11 and a plurality of the casings 26 may be disposed. The wall 17 is not limited to an annular or a circular shape, but it may be of a rectangular shape. That is, as far as the wall 17 serves as a jig that regulates the flow of resin when sealing by a resin member, the wall 17 may be formed in any shape.

As far as the resin member 27 covers the entire electronic component 19 in the casing 26, the resin member 27 may be formed in any shape. The second metal plate 25 may be made of a metal plate that simply serves as a connection layer. That is, the second metal plate may dispense with thermal stress relieving part such as the aforementioned step, groove or recess. 

What is claimed is:
 1. A motor-driven compressor including a semiconductor device, comprising: a compression mechanism; a motor driving the compression mechanism; a housing accommodating therein the compression mechanism and the motor; a wall extending from an outer surface of the housing so as to surround a part thereof and have an opened end, the wall cooperating with the outer surface of the housing to form a casing; an electronic component accommodated in the casing and including a semiconductor module, the semiconductor module including a circuit board connected to the outer surface of the housing and a semiconductor element mounted to the circuit board; and a resin member sealing an entirety of the electronic component in the casing.
 2. The motor-driven compressor according to claim 1, wherein the circuit board has a stress reducing part for reducing stress of a connection between the circuit board and the semiconductor element and a connection between the circuit board and the housing.
 3. The motor-driven compressor according to claim 1, wherein the circuit board is brazed to the housing. 